Depressive and anxiety disorders are each associated with significant impairment and disability and when they co-occur (which happens at alarmingly high rates) are especially harmful and difficult to treat. In order to develop more targeted treatments, it is essential to understand the core disease processes that underlie these two conditions as these processes may be why they co-occur so often. This study seeks to evaluate two tendencies that have been proposed to underlie depression and anxiety, respectively - low sensitivity to appetitive stimuli and high sensitivity to aversive stimuli. Depression has been associated with a reduced tendency to approach or seek out rewards or other positive stimuli (i.e., low sensitivity to appetitive). Anxiety disorders have been associated with a hyper-sensitivity to threatening or aversive stimuli. An important question, though, is whether low approach motivation is specific to depression and/or whether hyper-sensitivity to threat/aversiveness is specific to anxiety. A related question is whether these emotional tendencies are shared by depression and anxiety and relate to the high co-occurrence rates between the two conditions. The current study seeks to examine these questions by looking at behavioral and biological measures of these processes in individuals with depression, anxiety, or co-occurring depression and anxiety. Four groups of 29 individuals will participate - those with depression and anxiety, those with depression only, those with anxiety only, and a non-depressed/non-anxious control group. Each participant will undergo an assessment consisting of a clinical interview and questionnaires assessing personality and emotional/motivational tendencies. Additionally, we will examine putative biological markers for low appetitive motivation (asymmetries in EEG activity) and high sensitivity to threat/aversiveness (abnormal startle eyeblink response). The project has five specific aims - 1) Test the hypothesized association between depression and low approach motivation by comparing the EEG asymmetries of controls and depressed individuals while they anticipate the possibility of receiving a reward (money);2) Test the hypothesized association between anxiety and high aversiveness sensitivity by comparing the startle eyeblink responses of controls and anxious individuals while they anticipate the possibility of receiving an aversive/threatening stimulus (shock);3) Test whether low approach motivation and high aversiveness sensitivity are independent;4) Test whether low approach motivation and high aversiveness sensitivity are specific to depression and anxiety, respectively;and 5) Test whether the co-occurrence of depression and anxiety is due (or at least relates) to processes that are common to both conditions. In sum, the proposed study has the potential to provide important information regarding the emotional and biological mechanisms that underlie depression, anxiety and their co-occurrence. PUBLIC HEALTH RELEVANCE: Depressive and anxiety disorders are each associated with significant impairment and disability and when they co-occur (which happens at alarmingly high rates) are especially harmful and difficult to treat. In order to develop adequate treatments for these conditions, it is important to understand the processes that cause them and to examine potential abnormalities that may lead to their co-occurrence. This study will examine two emotional abnormalities/tendencies that have been related to depression and anxiety - a reduced sensitivity to pleasure and an over sensitivity to aversiveness or threat.